This invention relates to a capacitor. More particularly, this invention relates to a capacitor having polyphenylenesulfide (hereinafter referred to as PPS for short) film as at least a portion of the dielectric material of the capacitor.
I. Description of the Related Art
PPS film is disclosed, for example, in U.S. Pat. No. 4,286,018 and is known to have excellent properties as dielectric material of a capacitor. For example, a capacitor having PPS film as the dielectric material, which has excellent heat resistance, frequency characteristics and temperature characteristics, is disclosed in U.S. Pat. No. 4,672,506. In the conventional PPS film capacitor, aluminum thin layer is often formed on the PPS film by vapor deposition method and serves as an electrode.
However, the conventional aluminum-metallized PPS film capacitors have the drawbacks in, for example, that they have poor humidity resistance. That is, if the capacitor is used under high temperature and high humidity, the aluminum electrode rapidly fades away. As a result, the capacitance of the capacitor is decreased and the dielectric loss is largely increased.
To overcome this problem, a capacitor having PPS dielectric film with a specific surface roughness is proposed in Japanese Patent Disclosure (Kokai) No. 203315/87. Also proposed is a capacitor having PPS dielectric film with a specific surface tension so as to improve the adhesion between the PPS film and the aluminum electrode deposited thereon, which is disclosed in Japanese Patent Disclosure (Kokai) No. 226612/87.
However, even in these capacitors, the humidity resistance is not satisfactorily improved, and even if the capacitor is enclosed in an encapsulation in order to shut out the humidity, the humidity resistance may not be improved Further, in the conventional capacitors in which the adhesion between the PPS film and the deposited aluminum thin layer electrode is enhanced, or the intimacy among the PPS film layers of the wound or stacked PPS film(s) is enhanced, satisfactory humidity resistance is not obtained.